Thermostat



June 30, 1936. w SAUL 2,046,187

THERMOSTAT Filed Aug. 22, 1954 2 Sheets-Sheet l Jpine 30, 1936. w A L 2,046,187

THERMOSTAT Filed Aug; 22, 1954 2 Sheets-Sheet 2 Patented June 30, 1936 UNITED STATES.

PATENT OFFICE THERMOSTAT Waldo A. Saul, Lexington, Mass., assignor to General Plate Company, Attleboro, Mass., a corporation of Massachusetts This invention' relates to thermostats, and

' with regard to certain more specific features, to

thermostats having associated therewith an'element or combination of elements adapted to effect a control in a new manner.

I Among the several objects of the invention may be noted the provision ofa thermostat of the class described having associated therewith, in

a new manner, an element or combination of elements whereby the change of curvature of the thermostat in response to temperature variation is translated into a utilizable movement; and

a thermostat of the class described in which the said relative movement is utilizable to perform a variety of functions, such as signal, valve, and switch operation and the like. Other objects will be in part obvious and in part pointed out hereinafter.

'I'heinvention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which are illustrated several of various possible embodiments of the invention,

Fig.1 is a trimetric view of one embodiment of the invention;

Fig. 2 is a trimetric view similar to Fig. 1,, position of oppoa;

showing the thermostat in its site curvature;

Fig. 3 is a top plan view of the thermostatof '-"*i in Fig. 2. It is assumed that the plate is initially Fig. 1;

Fig. 4 is a Fig. 2;

a Fig. 5 is a cross section through the thermo-'; stat of Fig. 1, taken substantially along lines 55 of Figures 1 and 3;

Fig. 6 is a cross section similar to Fig. 5; ill'ustrating a position of the thermostat intermediate the Fig. 5 and Fig. 7 positions;

Fig. 7 is a crosssection through the thermostat of Fig. 2, taken substantially along the lines 'l'! of Figures 2 and 4.

Fig. 8 is a trimetric view of a second embddi ment of the invention;

Fig. 9 is a trimetric' view of a third embodiment of the invention;

Fig. 10 is a cross section through the thermo stat of Fig. 9, taken-substantially on line lll|0 of Fig. 9;

Fig. 11 is a cross section similar to Fig. 10, but illustrating the thermostat of Fig. 9 in an alternative position;

top plan view of the thermostat of Fig. 12 is a trimetric view of a fourth embodiment of the invention;

Fig. 13 is a cross section of a fifth embodiment of the invention, taken substantially along line l3-l3 of Fig. 16;

Fig. 14 is a cross section similar to Fig. 13, illustrating that embodiment in a more advanced position, and taken substantially along line l 4-] 4 of Fig. 17;

Fig. 15 is a cross section similar to Figures 13 10 and 14, illustrating that embodiment in a still more advanced position, and taken substantially along line l5|5 of Fig. 18;

Figures 16, 17 and 18 are front elevations of the Fig. 13 embodiment, corresponding in position, 15 respectively, t Figures 13, 14 and 15; and

Fig. 19 is a cross section similar to Fig. 13, but illustrating an electrical switch (sixth) embodiment of the invention.

Similar reference characters indicate corre- 20 sponding parts throughout the several views of the drawings.

In the group comprising Figures 1 through 7, numeral l indicates a sheet or strip or plate of composite thermostatic material, such as bimetal. In the example shown, the upper portion 3 of the plate I comprises a metal having a a relatively high c'oefiicient of thermal expansion, while the lower portion 5 comprises a metal having a relatively low coefiicient of thermal expansion. Hence, when the temperature rises, the plate I will exhibit a tendency to change its curvature from that shown in Fig. 1 to that shown formed, for the respective low temperature at which it is to operate, with the curvature shown in Fig. 1.

Struck from'the plate I are three loops 1, 9, and H, which serve as retainers for a bent wire l3. The loops 1, 9, and H do not lie in a straight 40 line; that is to say, loop 9 (the central loop) is displaced sidewardly from a straight line connecting loops 7 and H when the plate I is fiat. The wire I3 is of such a diameter, and is so bent, that it passes under the loops 1, 9, and II. It is not necessarily shaped so as to lie on the surface of the plate I between the loops, but may be the wire l3 in relatively close confinement, permit it a slight degree of lateral freedom inmovement relative to the plate I, as will be pointed out more particularly hereinafter.

Extending at right angles from the wire i3 is welded or otherwise immovably aflixed a wire i5,

- face having a curvature.

which carries on its end a signal flag ill. The wire it and flag ill serve herein as exemplary of the various objects or elements that may be attached. to the thermostat to be controlled thereby. They may be replaced, for example, by a movable contact assembly adapted to cooperate with a fixed contact to effect circuit control, or bya rotatable mercury switch (such as is shown, in connection with another embodiment of the present invention, in Fig. 19).

In connection with the operation of this embodiment of the invention, certain of the theoretical aspects underlying the present invention will be pointed out. The bimetallic plate l, for example, may beconsidered as a mathematical sur- For purposes of definition, it will be stated that a normal to this mathematical surface is a line intersecting the surface and perpendicular to a plane tangent to the surface at the point of intersection. Any plane that contains this normal line is call-ed a normal plane, and the line of intersection of this normal plane with the surface is called a normal section of the surface. sects the surface and which contains no normal lines, is termed an oblique. plane, and the line of surface is called an oblique section of the surface.-

. for reasons to be advanced hereinafter).

intersection of such an oblique plane with the Now, it is a mathematical proposition that, if it is possible at all (depending upon the nature of the given curve), a plane may be passed through a given point on a surface so as to cut that surface in the form of a given'curve having an assigned form only by taking the cutting plane, in general, in a definite position.

The invention embodies the above-stated geometry. The axial lineal element, or wire it, is hypothetically a curve of assigned form or forms, and, by reason of its articulation to the bimetallic plate I (the curved surface), it corresponds to a section curve of the surface. The

wire l3, if it is a plane curve, determines a plane which is an oblique plane (it cannot be normal Since the wire is substantially stiff, the shape of the curve of the wire l3 can be altered only within limits. However, the shape (or curvature) of the plate 1 does alter in response to temperature changes. In the abstract, mathematical sense, a second form or curvature. of the plate I is a new surface, and, in order that the shape curve of the Wire l3 shall conform to this new surface and to an oblique section thereof, or parallel to the oblique section but displaced therefrom, it is necessary that the hypothetical oblique plane containing the wire l3 shall move to a new positionof obliquity, the motion involving a rotation through a definite angle determined by the extent of change of curvature of the plate l.

Expressed concretely, this rotation of the hypothetical plane to a new angle of obliquity is a ro- Y tation of the wire I3 relative to the plate i,-with complete lineal section of the curved plate 8-,

there'is practically no need for it to be complete it being sufficient that it comprise three points of contact with the plate A (the loops l, 9, and H) because three points'geometrically serve to locate definitely their corresponding oblique section of the plate I and in addition also define the oblique, hypothetical plane which changes its angleof obliquity. Hence, from a of the curved plate l.

Any plane which interpractical standpoint, the shape of the wire is intermediate the points i, t. and ii is of no-consequence, so long as the points i, 9, and l l lie in the desired oblique section of the plate l.

The points if, 9, and H should lie in a plane determining an oblique, and not a normal section The reason for this may be made clear by pointing out the objection to a normal section. A normal section, theoretically at least, would produce a-dead center condition; the lineal element so positioned would resist relative movement between it and the curved surface, the normality producing, instead of a force tending to produce a relative movement, a force tending to press the lineal element and the curved surface more closely together. This condition would be one of instability, because a slight disturbance or malformation in either direction would initiate the motion, which might then with equal probability be in either direction, and hence not practically utilizable. However, a definite obliquity in one direction, no matter how small, causes the action to be direct, positive, and uni directional, and hence practically utilizable.

From the above considerations, it will be seen that the invention comprises an element, the cur vature of which changes in response to temperature variations, and a second element containing at least three points articulated to the first element and prevented from assuming a straight-line relationship with respect to each other, the three points defining a plane which cuts an oblique sec tion on the plate l except when the plate I is itself hat. Under the latter condition the plane of the points may lie in a plane parallel to the plate.

The practical operation of this embodiment of the invention may be summarized as follows: Since no end confinements are provided for the plate l, in the present embodiment, its change of curvature from the Fig. 1 form to the Fig. 2 form will be gradual, and continuous. This means that the tendency of the plate I, as it starts from its Fig. 1 position, will be-to straighten or flatten out. Since the wire I3 is journalled to the plate in the Fig. 1 position, it will undergo a rotation about a hypothetical axis connecting the loops '1 and I l, to compensate for the change of curvature of the plate I. Then, as the plate I passes from fiat position to the position of reverse curvature. shown in Fig. 2, this rotation of the wire l3 will continue in the same direction. This rotation of the wire l3 relative to the plate I will be seen more clearly in Figures 5, 6, and '7. Fig. 6 also illustrates the condition of the three points positioned in a plane parallel to the plane of the sheet or plate. The rotation of the wire l3 causes angular movement of the wire l5, and the signal I! is thus moved from one side to the other. Nodead center condition'is presented so long as the plane of the three points is not normal to the plate.

The embodiment of the. invention thus far described is slow-acting; that is, it has, between its extreme positions, anindefinite number of relatively stable intermediate positions each corresponding to a. definite ambient temperature. It is useful, forexample, as a thermometer, if the flag ll be replaced by a pointer, and a suitable temperature, the plate I stores its energy until it has accumulated suflicient, whereupon it snaps or moves substantially instantaneously to its position of opposite curvature. Thus the flag I! is moved instantaneously between its two extreme positions. It will be understood, of course, that the wire I3, etc., are provided in this embodimentin the same form and manner as in the Fig. 1 embodiment.

The transformation of a slow-acting strip or plate of composite thermostatic material into a snap-acting strip or plate, in the above manner, is treated at length in John A. Spencer Patent Nos. 1,602,510 and 1,813,776. and in EIi'E. Gregory Patent No. 1,845,998.

In Figures 9, 10, and 11 is shown the adaptation of the invention to a non-developable, dished theromstatic disc 25, which is by itself the subject of John A. Spencer Patent No. 1,448,240. The wire I3 is now applied to the disc 25 in an approximately diametrical manner; that is, the

loops 1 and i l are at diametrically opposite points on the disc 25, but the loop 9 is displaced from the geometrical center of the disc a slight, amount in order that it will not lie on the diametrical straight line connecting the loops l and II, thus again determining an oblique, rather than a normal section of the curved surfacerepresented by the disc 25. The disc 25 moves, with changing temperature, from a curvature or dishing in one direction, to an opposite dishing or curvature, with a snap action, in accordance with the teachings of Patent No. 1,448,240. In so doing, it rotates the wire I3 and moves the signal I'l in much the same manner as the Fig. l embodiment.

In all of the embodiments heretofore described, the plate I has been madeof composite thermostatic material. It is not essential that this be so in all cases. Fig. 12, for example, illustrates an embodiment of the invention in which the plate 5 is a monometallic resilient sheet, such as spring brass or steel. The wire I3 and signal flag ii are mounted thereon by the loops i, 3, and H in the same manner as in the Figures 1 and 8 embodiments; in fact, the support it! in the present embodiment is the same as the support of the Fig. 8 embodiment. Between the support it and the central region of the plate I] there reacts a U-shaped bimetallic strip 59, the strip 59 being attached at one end to the support and at the other end to the plate i. As the temperature rises, the U-shaped strip tends to open out; this it can do only by overcentering the plate l to a position of opposite curvature. On cooling, the reverse action takes place, the ends of the strip 59 tending to come together to overcenter the plate l back to the Fig. 12 position. The motions of plate i are thus identical to those of a bimetallic plate, and the wire I3 is thus rotated in the same manner as in the Fig. 8 embodiment. Thus it will be seen that the present invention covers .an embodiment wherein the curvature-changing element is not capable of thermostatic movement by itself, but is activated to change its curvature by an outside temperature responsive element.

Pressure responsive elements could be used equally well, or elements responsive to other changes.

The U-shaped bimetallic strip 59 is itself exthat might be employed. For example, a gas or fluid-filled bulb and bellows system might replace the strip 59, or a rod-and-tube thermostat. Other thermally or pressure susceptible devices too numerous to mention might also be employed. In all of the embodiments heretofore described, the wire I3 has been considered as the movable, and the plate I the stationary element of the couple. In .the embodiment of the invention shown in Figures 13 through 18, the reverse is the case, the wire I3 now being relatively stationary, and the plate I relatively movable. This relationship is achieved by embedding or otherwise suitably holding the end of wire I5 in a stationary base 63, and leaving the plate I free for movement. The parts are otherwise the same as in the Fig. 1 embodiment of the invention, except that the signal I1 is mounted on a projection 65 extending from the plate I. The operation of this embodiment is the same as that of the Fig. 1 embodiment, with the exception that the wire I3 is now stationary while the plate I undergoes 'ooth change of curvature and rotary movement around a hypothetical axis passing through the loops 1 and II. The coextensive change of shape and rotary movement of the plate I is indicated by the successive sectional views, Figures 13, 14, and 15, and the successive elevational views, Figures 16, 17, and 18. The embodiment may obviously be made snap-acting, in any of the manners heretofore described, if desired.

Similarly, the various snap-acting embodiments of the invention heretofore described may likewise be made in accordance with the teachings of the Fig. 13 embodiment, by fixing the angular position of the rotating wire and permitting the plate to undergo both the rotation and the change of shape about the wire. For example, the wire I5 of the Fig. 9 embodiment may be held rigid, thereby forcing the disc 25 to rotate about the wire it].

It will be noted that when a wire or bent shaft is used its disposition between the three points must be such that it will not interfere with the change of curvature of the plate 4.

In all of the embodiments heretofore shown and described, the useful work of the thermostat has been either as a signal or, impliedly, as a control such as a valve. It will be obvious that the relative movement characteristic of the invention may likewise be employed for the actuation of an electric switch. As exemplary of this feature of the invention, Fig. 19 shows the embodiment of Fig. 13 with the signal flag I? thereof replaced by a mercury switch 55 carried directly on the plate l. Upon change of position (rotation) of the plate 9 in response to temperature changes, the switch 55 is rotated, thereby moving the pool of mercury indicated by numeral 51 to make and break contacts. It is obvious that other forms of electrical contacts may well be used, and that this or any other forms of electrical contacts may be applied to the other embodiments of the invention.

shown in the drawings, the extent of curvature of the various thermostatic elements has been exaggerated relative to their size, in order more clearly to show the efiects of the change of ourvature. In practical embodiments of the invention, these curvatures are relatively slight.

It is also to be noted that the thicknesses of the plates throughout the drawings have been greatly exaggerated with respect to the sizes of the plates, in order to show more clearly their bimetallic construction, where such (specifically) is used.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in carrying out the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. J

I claim: 1

1. A thermostat comprising means the curvature of which changes in response to temperature variations, and second means articulated to said first means, said second means containing three spaced points determining a non-normal plane to the first means, said three points always maintaining a non-linear relationship.

2. A thermostat comprising means, the curvature of which changes in response to temperature variations, and second means articuiated to said first means, said second means containing at least three spaced points, said points determining a hypothetical plane which is oblique to the first means at certain temperatures, said three mints never reaching a straight line position with respect to each other during cha es, of curvature of said first means, whereby, upon change or curvature of said first means, the angle of obliquity of said hypothetical plane changes.

3. A thermostat comprising a plate of composite thermostatic metal, the curvature of which changes in response to temperature variations, and which at one temperature is substantially flat, an element of substantially lineal form articulated to said plate at at least three spaced points, said points at certain temperatures determining an oblique sectionof said plate, and at said one temperature lying in a plane parallel to the plane of the plate; said three spaced points comprising means securely attached to said plate, whereby, upon changes of curvature of said plate, relative rotary motion is had between said plate and said lineal element.

4. A thermostat as set forth in claim 2, in which the thermostatic plate comprises a non-developable disc.

5. A thermostat as set forth in claim 2, in which the first means is relatively fixed in position, whereby the second means undergoes movement;

6. A thermostat as set forth claim 2, in whichthe second means is relatively fixed in position, whereby the first means undergoes movement.

'7. A thermostat as set forth in claim 2, in which the means articulating the first and second means together permit a degree of lateral lostmotion between said first and second means.

aci ic? A thermostat comprising a plate of composite thermostatic material, an element, means connecting said element to said plate at the extremities of said plate, and additional means connecting said element to a central point on said plate, said central point being displaced from a normal plane passing through the two 'outer points of contact of said element with said plate.

9. A thermostat comprising a plate of composite thermostatic material, an element, means connecting said element to said plate at the extremities of said plate, and additional means connecting said element to a central point on said plate, said central point being displaced from a normal plane passing through the two outer points of contact of said element with said plate, at least one of said connecting means providing for a limited degree of lateral lost-motion between said element and said plate.

10. A thermostat comprising a plate of composite thermostatic material, an element, means connecting said element to said plate at the extremities or said plate, and additional means connesting said element to a centralpoint on said plate, said central point being displaced from a normal plane passing through the two outer points of contact of said element with said plate said plate being held in a relatively fixed position, whereby, upon change of curvature of said plate incident to variation of external. temperature,

said element is forced to rotate.

ll. A thermostat comprising a plate of composite thermostatic material, an element, means connecting said element to said plate at the extremities of said plate, and additional means connecting said element to a central point on said plate, said central. point being displaced from a normal plane passing through the two outer points'of contact of said element with said plate, said element being held in a relatively fixed position, whereby, upon'change of curvature of said plate incident to variation of external temperature, said plate is forced to rotate about said element.

12. A thermostat comprising a. plate of composite thermostatic material, an element, means conmeeting said element to said plate at the extremities of said plate, and additional means connecting said element to a central point on said plate,

said central point being displaced from. a. normal plane passing through the two outer points of contact of said element with said plate, said plate being in the form of a dished'disc, whereby it is adapted, upon change of external temperature, to snap into a position of opposite curvature.

13. A thermostat comprising a plate of composite thermostatic material, an element, means connecting said element to said plate at the extremities of said plate, and additional means connecting said element to a central point on said plate, said central point being displaced from a. normal plane passing through the two outer points of contact of said element with said plate, said plate being in the form of a dished disc, whereby it is adapted, upon change of external temperature, to snap into a position of opposite curvature, said disc being held in a relatively fixed position, whereby, upon reversal of curvature of said disc, said element is forced to rotate.

' WALDO A. SAUL. 

